Sunday, May 6, 2018

Anglerfish, with their menacing gape and dangling lure, are among the
most curious inhabitants of the deep ocean.
Scientists have hardly ever
seen them alive in their natural environment.

That’s why a new video,
captured in the waters around Portugal’s Azores islands, has stunned
deep-sea biologists.
It shows a fist-size female anglerfish, resplendent
with bioluminescent lights and elongated whiskerlike structures
projecting outward from her body.
And if you look closely, she’s got a
mate: A dwarf male is fused to her underside, essentially acting as a
permanent sperm provider.
“I’ve been studying these [animals] for most of my life and I’ve
never seen anything like it,” says Ted Pietsch, a deep-sea fish
researcher at the University of Washington in Seattle.

Most of what we know about deep-sea anglerfish comes from dead
animals pulled up in nets.
Scientists have identified more than 160
species, but only a handful of videos exist—and this is the first to
show a sexually united pair.
“So you can see how rare and important this
discovery is,” Pietsch says.
“It was really a shocker for me.”

The video was captured at a depth of 800 meters by deep-sea explorers
Kirsten and Joachim Jakobsen in a submersible.
The husband and wife
team was nearing the end of a grueling 5-hour dive along a steep
deep-sea wall on the south side of São Jorge Island, when “something
with a funny form” caught their eye, Kirsten Jakobsen says.
Aborting
their plan to surface, the filmmakers followed the strange creature
around for 25 minutes, capturing its movements through the submersible’s
1.4-meter-wide window.
It was exciting, but also challenging to
maneuver the craft to get the best images because the female was only
about 16 centimeters long, she says.
After surfacing, the duo sent the video to Pietsch, who identified the species as Caulophryne jordani,
known as the fanfin angler. He was entranced by the species’s
“gracefulness,” especially the way those whiskerlike structures—called
filaments and fin rays—enveloped the animal. “Any prey item touching one
of those would cause the angler to turn and gobble up that particular
animal,” he says.
“They can’t afford to let a meal go by because there’s
so little to eat down there.”

The video was captured in August 2016,
but this is the first time it’s been released to the public. C. jordani’s light show was also a stunner.
Like other
deep-sea anglerfish, the female has a bioluminescent, lurelike appendage
that drifts in front of her head to attract prey.
But in the video, the
filaments and fin rays also appear to emit light at their tips and at
intervals along their length—something that’s never been seen before.
Pietsch suspects that the light is bioluminescent—meaning, it’s produced
within the animal itself—but he notes that it’s hard to know whether
the structures are reflecting light from the submersible or are actually
glowing.

The tiny male is also a key part of the discovery.
Like many other species of anglerfish, C. jordani forms
a permanent pair bond—once a male finds a mate, he bites into her,
eventually fusing with her tissue and gaining sustenance through her
blood stream.
Scientists have known about this bizarre reproductive
strategy because they’ve seen dead males latched onto dead females, but
people have never seen it in the wild—until now.

Bruce Robison, a deep-sea ecologist at the Monterey Bay Aquarium
Research Institute in Moss Landing, California, was impressed with how
flexible the male was despite its solid attachment, seemingly moving
around in any direction he wished.
“There’s no way I would have ever
guessed that from a [museum] specimen.”
Anglerfish are an incredibly diverse group, with “a marvelous variety
of structures and species,” but they’re hard to study because they
dwell hundreds to thousands of meters below the surface of the ocean,
says Peter Bartsch, a fish scientist at the Natural History Museum in
Berlin.
With recent advances in deep-water exploration technology, he
adds, videos like this are much more possible, giving us a better idea
about what these mysterious creatures actually look like in their deep,
dark home.